/* 程序10-22 如何处理SIGTSTP */
#include <signal.h>
#include <unistd.h>
#include <stdio.h>

#define	BUFFSIZE	1024

static void sig_tstp(int);

int main(void)
{
	int n;
	char buf[BUFFSIZE];

	/* only catch SIGTSTP if we're running with a job-control shell */
	if (signal(SIGTSTP, SIG_IGN) == SIG_DFL)
		signal(SIGTSTP, sig_tstp);

	while ((n = read(STDIN_FILENO, buf, BUFFSIZE)) > 0)
		if (write(STDOUT_FILENO, buf, n) != n) {
			perror("write error");
			exit(1);
		}
	if (n < 0) {
		perror("read error");
		exit(1);
	}

	exit(0);
}

static void sig_tstp(int signo)		/* signal handler for SIGTSTP */
{
	sigset_t mask;

	/* ... move cursor to lower left corner, reset tty mode ... */

	/* unblock SIGTSTP, since it's blocked while we're handling it */
	sigemptyset(&mask);
	sigaddset(&mask, SIGTSTP);
	sigprocmask(SIG_UNBLOCK, &mask, NULL);

	signal(SIGTSTP, SIG_DFL);	/* reset disposition to default */

	kill(getpid(), SIGTSTP);	/* and send the signal to ourself */

			/* we won't return from the kill until we're continued */

	signal(SIGTSTP, sig_tstp);	/* reestablish signal handler */

	/* ... reset tty mode, redraw screen ... */
	return;
}
